The best turn around I did at domestic was 16 minutes from shutdown to startup... That said, we ferried the plane in empty and departed back to Sydney with relative urgency (i.e.: it was Friday night and we all wanted to go home). 25-30 minutes would be the usual for domestic.
There's no real time pressure at long haul (in my operation anyway) as they're all one sector days. I usually aim to arrive at the airport 2 hours prior and get to the plane at least 1 hour prior
